Project Summary Humans with post-traumatic stress disorder (PTSD) are more likely to develop alcohol use disorder (AUD) than the general population, and AUD is the most commonly co-occurring mental health disorder in humans with PTSD. These conditions, separately and combined, affect millions of American, cause millions of deaths worldwide, and cost society billions of dollars. This proposal will examine individual differences in traumatic stress effects on specific brain circuits in male and female alcohol drinkers, and will manipulate those circuits to test their role in post-stress escalation of alcohol drinking. Here, we focus specifically on amygdala disinhibition and endocannabinoid signaling, but we will collect blood and brain samples that allow for subsequent analysis of predictive biomarkers, as well as follow-up experiments in alternate brain circuits. This project falls within the scope of the NIAAA mission to support biological and behavioral research underlying addictive behaviors. More importantly, the current proposal addresses the research objectives outlined in RFA-AA-17-016 by assessing alcohol drinking in a well characterized animal model of PTSD, determining the association of pre-stress alcohol drikning with the development of post-stress escalation of alcohol drinking, systematically testing the effect of sex on post-stress escalation of alcohol drinking, identifying neurobiological processes that underlie the transition to post-stress escalation of alcohol drinking, and identifying neurobiological targets for potential treatment of alcohol abuse in PTSD patients. Specifically, this application proposes the use of rat models to examine the neurobiology underlying stress-induced escalation of alcohol drinking in male and female animals. This application proposes the use of behavioral, electrophysiology, biochemistry, and molecular biology techniques to identify brain circuits altered by traumatic stress in subsets of alcohol drinkers, and to directly test the role of those circuits in escalated alcohol drinking after stress. The overall goals of the proposed work are to test the role of 1) amygdala disnihibition and 2) brain endocannabinoid signaling in traumatic stress-induced escalation of alcohol drinking in a stress-susceptible subpopulation.